1. Voice over IPVoice over IP
Habib UllahHabib Ullah
12-MS-CSc-1212-MS-CSc-12

2. Contents
 Abstract
 What isVoIP
 HowVoIP works
 VoIP Architecture
 Components
 Pros & Cons
 Summary

3. Abstract
 Voice over Internet Protocol
(VoIP) is a technology that
enables one to make and
receive phone calls through
the Internet instead of using
the traditional analogy
PSTN (Public Switched
Telephone Network) lines.

4. What is VoIP?
 VoIP is packetisation and transport of
classic public switched telephone system
audio over an IP network.
 It allows 2-way voice transmission over
broadband connection.
 It is also called IP telephony, internet telephony, voice over
broadband, broadband telephony.

5. PSTN vs. INTERNET
PSTN
 Voice network use circuit
switching.
 Dedicated path between
calling and called party.
 Bandwidth reserved in
advance.
 Cost is based on distance
and time.
INTERNET
 Data network use packet
switching.
 No dedicated path between
sender and receiver.
 It acquires and releases
bandwidth, as it needed.
 Cost is not based on
distance and time.

6. PBX
Yesterday’s Networks
Circuit Switched Networks (Voice)
CO
PBX
CO
CO
Packet Switched Networks (Data)
Router
Router
Router
Router
Router
• Separated networks
• Separated applications/services

7. PBX
IP Phone
Converged Network
PSTN
CO
Gateway
Router
Router
Router
Router
• Converged network
• Separated or integrated applications
PBX
IP Phone

8. VoIP – How does it work?
 Converting the voice signal
 ADC (analog to digital)
 DAC (digital to analog)
Voice (source) - - ADC - - - Internet - - - DAC - -Voice (dest)
 Transmission of voice traffic in packets

9. VoIP – How does it work?
 The 1-2-3s of VoIP
 1. Compression – voice is compressed
typically with one of the following codecs, G7.11
64k, G7.29AB 8k, G723.1 6.3k
 2. Encapsulation – the digitized voice is
wrapped in an IP packet
 3. Routing – the voice packet is routed thru
the network to its final destination

10. LT
S©Telcordia Technologies, Inc. Slide 10
IP Network
Multimedia
PC
Multimedia
PC
Initially, PC to PC
voice calls over the
Internet
VoIP Architecture?
PSTN
(DC)
Gateway
PSTN
(NY)
Gateway
Public Switched
Telephone Network
Gateways allow PCs
to also reach phones
…or phones to reach
phones

11. Components
 VoIP Protocols
 VoIP Gateway
 VoIP Codecs

12. VoIP Network Model
SIP
RTP, RTCP, RTSP
Transport Layer (UDP, TCP)
Network Layer (IP, IP Multicast)
Data Link Layer
Physical Layer

13. PURC
IP Protocol LayeringIP Protocol Layering
Physical Transport (e.g, Cable Modem)
IP (Internet Protocol)
TCP UDP
Applications (e.g., email, web pages)
Email Data (1000 bytes)TCP Header
(20 bytes)
IP Header
(20 bytes)
A Typical IP Datagram

14. VoIP SIP

16. VoIP Gateway
 A VoIP gateway is a gateway device that uses Internet
Protocols to transmit and receive voice communications
(VoIP).

17. VoIP Codecs
 Codecs are used to convert an analog voice signal to
digitally encoded version. Codecs vary in the sound
quality, the bandwidth required, the computational
requirements, etc.

18. Do Companies Want VoIP?
76% Will!76% Will!
Unsure
4%
Not at all
likely
4%
Not very
likely
16%
Likely
28%
Very likely
32%
Extremely
likely
16%
Network World asked 500 readers to assess
whether they would consider using voice over IP:

19. Key Business Drivers for LAN-Based Telephony and VoIP
81%81%
59%59%
38%38%
26%26%
0 50 100
Save MoneySave Money
Better Utilization of BandwidthBetter Utilization of Bandwidth
Support MultimediaSupport Multimedia
Improve Network ManagementImprove Network Management

20. Security Risks
 AsVoIP uses the Internet, for example, it is vulnerable to
the same type as security risks
 Hacking
 Denial of service
 Eavesdropping

21. Summary

22. Questions?